The newly updated map provides a better tool for visualizing the distribution of carbon stocks, which are dominated by soil stocks in some parts of the world such as boreal peatlands and tropical swamps. Further improvements could be achieved by incorporating updated biomass carbon estimates derived from 2005 land cover data (currently under review in draft form) and by potentially considering the likely effects of land use change on soil carbon stocks.

A global map of estimated soil carbon stocks to 1m depth was generated based on the soil organic carbon and bulk density values included in the HWSD (FAO/IIASA/ISRIC/ISS-CAS/JRC 2009), adjusting for gravel content and taking account of variations in soil depth. The data in the HWSD were quality checked, incorrect values were adjusted and missing data filled in where possible. Many of these data are based on the FAO 1974 soil mapping units, which are much larger polygons that have been rasterised at 1km resolution. These estimates reflect inherent soil properties at the time of the original survey, but do not take account of land use change.